diff --git a/dart/freeform-gradient/README.md b/dart/freeform-gradient/README.md
index f3a02b3..5401909 100644
--- a/dart/freeform-gradient/README.md
+++ b/dart/freeform-gradient/README.md
@@ -52,7 +52,7 @@ After this, enter into your nix-shell and you are good to go.
 ### To update the whole environment, do the following in order:
 
 - `niv init` will update nix/sources.nix if a new one is available
-- backup your nix/sources.json: `cp nix/sources.json nix/sources.json.bak`
+- Make sure you have a backup of your nix/sources.json. If you're not in a git repo or use another vcs: `cp nix/sources.json nix/sources.json.bak`
 - `niv update` will update sources.json i.e. your version of nixpkgs used in this environment
   - you may need to edit nix/android.nix if any of the attributes in there can't be found after this.
 - `direnv reload` will rebuild/reload your environment (may not be necessary if it automatically reloads)